Components of fluid flow engines, and particularly the blades thereof, which are made of fiber reinforced synthetic composite materials and which are exposed to the fluid flow within the engine, are subjected to dangerous erosion effects caused by abrasive particles in the fluid flow and by thermal load effects. In order to protect components of an engine, German Patent Laying Open Publication DE-OS 4,343,904 proposes to apply an erosion resistant inorganic lacquer coating onto the respective components. This known method has the advantage that it is relatively easy and cheap to apply and fire the lacquer coating onto the components, even as a repair method for used components. However, the reliability or durability of the adhesion of the lacquer coating onto the components has been found to be problematic, so that it may be necessary to repeat the application of the lacquer coating during the operating lifetime of the component. This increases the overall costs of the known method, and also entails an increased effort for inspection and maintenance.
As a further alternative, German Patent Publication DE-PS 4,208,842 describes an erosion protection for helicopter rotor blades made of fiber reinforced synthetic materials, wherein the critical locations of the rotor blade are covered or coated by a sheet metal member that is glued or otherwise adhered onto the surface of the rotor blade. Moreover, the sheet metal member is coated with particles of metallic compounds. In this case once again, the problem arises that the reliability or durability of the adhesion of the glued-on sheet metal with the underlying fiber composite structure is inadequate.
In order to protect composite blades against high impact loads, German Patent Publication DE 2,631,856 suggests a leading edge protection consisting of a wire mesh that is anchored in the fiber composite material of the main structure of the blade body. However, it is a disadvantage that such wire meshes have a relatively coarse mesh size, as limited by the minimum diameter of the wires that are used to make the mesh. Due to this relatively coarse mesh, the primary applicability of this known solution is to provide protection from the impact of relatively large foreign bodies, such as birds for example. Smaller foreign bodies can still penetrate and cause erosion of the fiber composite material in the coarse mesh spaces between the individual wires. Thus, this known solution is not very well suited for providing protection against erosion from sand and the like, for example.
U.S. Pat. No. 3,762,835 describes a further means for protecting the leading edges of composite blades, and particularly in relation to providing a foreign body impact protection for compressor blades. According to this patent, a layer of a fine wire mesh or net is arranged under the surface and extends over and around the leading edge of a fiber composite material compressor blade. This fine wire net layer arranged under the surface is coated with nickel and forms a protective layer against impact damage caused by large and small foreign bodies, such as stones and sand. If the net or mesh layer arranged under the surface is fixed by means of a non-sliding adhesive, the adhesive material in the interspaces of the net or mesh is coated with silver, and the adhesive material is bonded by means of atomic bonding with the nodes or knots of the net or mesh, which thus forms a metallic strip.
However, in individual cases in which the leading edges of blower or fan blades were provided with a foreign body impact and erosion protection comprising such metallic strips extending over and around the leading edges, it has been discovered in practice that the metallic strips can become at least partially delaminated or defoliated and removed from the blades, as a result of strikes or impacts by middle-sized birds. As a consequence, the protection is at least partially lost, and further damage of the fiber layers of the blades can no longer be prevented.